BONSPIEL

BONSPIEL is a curling match against a cagey AI skip — three ends, four stones a side, real curling scoring — built around the thing every other aiming game leaves out: in curling, the shot starts when you let go.

How to play

• Set your broom where you want the stone to travel and pick a handle — in-turn curls left, out-turn curls right.
• Hold to charge the weight meter. The bands are real curling calls: guard, draw, hack, takeout. Release to throw.
• Now scrub. While the stone runs, scrub your mouse (or rub the screen, or mash arrow keys) to sweep. Sweeping melts the pebbled ice ahead of the stone, so it runs farther and curls less. Your sweepers tire — the stamina bar means you spend sweep where it counts, and late sweep buys more than early.

Only the side nearest the button scores, one point per stone closer than the best opposing stone. Score an end and you give up the hammer. Tied after three ends goes to a sudden-death extra.

The twist

An unswept draw curls three or four stone-widths, most of it in the last few feet — so every shot is a negotiation you conduct after release. Under-sweep and it curls wide and dies short. Panic-sweep from the hog line and a nice draw sails out the back of the house. The skip across the ice isn't scripted, either: it simulates candidate shots through the same physics you play under — draws, takeouts, peels, guards — picks the best one, and sweeps its own stones on its own judgment. It also misses, because it throws with human noise. Beat it and you've earned the handshake.

How it was made

Made in one autonomous run: Claude Fable 5 designed the game and wrote this page; Claude Opus 5 built the whole thing as a single self-contained HTML file — fixed-timestep physics with a friction model that bites at low speed (that's what end-loads the curl), an AI that plays by simulating its options through the same step function, and synthesized WebAudio for the stone rumble, the sweep swish, and the knock of a takeout. It then auto-played roughly 250 headless matches against its own harness and fixed the fifteen-odd bugs that fell out before shipping.